Position indicating tools for subterranean use are illustrated in U.S. Pat. No. 7,284,606. The elements of this tool are a series of dogs that find a groove generally after passing that groove and being brought back up into engagement. Once the dogs engage a force is placed on the string. This force moves the string up against resistance of fluid that is forced from one reservoir to another through a restriction orifice. The orifice provides a time delay that is sufficiently long to realize at the surface that the tool is properly located before a release of the stress on the dogs in the groove starts to happen. The idea is that the delay is long enough to allow surface personnel to reduce the pulling force so that at the time there is a release the applied force on the dogs is also reduced.
In field applications there still seemed to be severe wear on the dogs causing them to have to be replaced at more frequent intervals than was desired. One of the problems was that surface personnel would forget or react too slowly in reducing the applied force at the time of release so that no decrease in the wear rate of the dogs could be achieved. Even if the applied pulling load was reduced at the time of release, there was still an issue of the hydraulic system still operating to force fluid through the orifice as relative movement between a mandrel being pulled on and the dogs still in the groove continued to stress the dogs as progressively less contact area supported the dogs in the surrounding groove as well as on the mandrel at a location under the dogs. Despite the reduced pulling force, the progressive decrease in contact support area on various locations on the dog as it was being released, increased those localized stresses. As a result pieces of the dog were still subject to overstress to the point where pieces of the dog near such overstressed local regions would simply be sheared off. This required frequent maintenance to the dogs generally by a replacement of parts.
Another issue with the prior tool was that if there were many indicating recesses in the wellbore, there was a possibility that the tool would engage them on the way out and to get the tool to release the same metering procedure as initially undertaken would need to be repeated. This could take time and that results in additional expense to the operator.
Other tools in the past that would only shift a given downhole sliding sleeve once and could not re-latch if the sleeve had been shifted close enough to a travel stop are shown in U.S. Pat. No. 5,636,694. However, there was no mechanism on the tool itself that kept it from re-engaging after a given sleeve shift. What prevented this tool from re-engaging a sleeve it had just shifted was that the sleeve in question had moved to the desired position. This tool would still engage other similarly configured sleeves as it had a reset capability.
The present invention improves on the design of the position locating tool in U.S. Pat. No. 7,284,606 and modifies it in several respects. It unloads the hydraulic system while the dogs are still sufficiently supported to minimize the shearing issues with the dogs. The unloading occurs with the dogs still sufficiently supported so that stress will not intensify at the time of release to the extent that localized failure can occur. An optional feature allows the tool to be a single time operation by disabling the metering system by virtue of holding the shifted position of parts after a single use so that the metering system is disabled and the tool is prevented from resetting. While the dogs can go into other recesses in the disabled condition, the metering system is not operative and the dogs will simply jump back out of any such grooves when a minimal uphole force is applied to the tool body on the way out of the subterranean location. These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is given by the associated claims.